Packaging containers, i.e. containers made out of a sheet of packaging material have been known for a long time in the packaging industry. The packaging material from which the container is raised usually consists of several layers fused together to form a packaging laminate. One typical composition of a packaging laminate is an outer polymer layer on top of a core layer of fiber-based material, such a carton and one inner polymer layer having the function of a liquid barrier towards the foodstuff to be contained. In some variants, a barrier layer, often aluminium foil, is sandwiched between two polymer layers on top of the core layer facing the interior of the container when raised. These types of packaging laminates are assembled into packaging containers in order to contain foodstuffs with a higher acidity or to provide longer shelf life for foodstuffs stored under ambient conditions.
Usually, blanks of a packaging laminate from which the packaging container is raised are provided on rolls and fed to a converting facility where they are cut into different webs, i.e. slitted, and provided with crease lines. The crease lines are weakening lines in the packaging laminate along which the blank can be folded and raised into a container. Since the cutting and creasing operations are well-known in the art, they will not be elaborated in detail here.
Once the blanks are raised into a container, the container is, depending on the type of packaging container, sterilized and later filled with the foodstuff to be contained.
Containers made from such blanks of packaging laminate are known under various brands, such as Tetra Brik™, Tetra Brik Aseptic™, Tetra Brik Edge™, Tetra Rex™ and so on.
In the course of development of newer types of packaging materials which require lesser amounts of paper and polymer, the packaging containers have become thinner and lighter than the originally developed ones leading to one problem emerging especially for packaging containers having volumes of 1000 ml and higher. The raised, filled and sealed packages show a bulging effect due to the weight of the foodstuff pressing on the relatively thin walls of the packaging container, making them more difficult to handle in distribution equipment and also unattractive in appearance both to producers and consumers alike. The problem of bulging has been in existence a number of years and several solutions have been developed to solve it.
One existing solution uses metal plates arranged on opposite sides of a conveyor belt engaging the packaging containers from the time they are raised until they are forwarded to the distributing equipment. This solution provides some reduction of the bulging effect, but still not satisfactory. One other disadvantage of the solution is that it is static and does not fit different package shapes and sizes.
One other solution is described in the U.S. Pat. No. 5,975,158A where a compression bar located inside a holder for gable top containers presses against the walls of the container during the time the container is sealed at its top end. This solution is similar to the previous one described and also has the same disadvantages, namely that the compression exerted on the container walls is static and not optimal for different container shapes and sizes. The final sealed gable top package may thus still display visible bulging for different container types.
There is thus a need for a solution providing a flexible way to minimize bulging for a variety of packaging container shapes and sizes in an optimum way.